1. Field of the Invention
The present invention relates to an exposure control device for a camera which detects a light reflected by a film surface after it has passed through an imaging lens in a normal photographing mode or flash photographing mode and controls the exposure based on the detected light.
2. Related Background Art
A light emission control system of an electronic flash device by a TTL (through-the-lens) direct light detection in which a light transmitted through a photographic lens is reflected by a film surface and a light emission duration of the electronic flash device is controlled in accordance with an integration of the reflected light so that the light emission is controlled has been commonly used as a control system for the light emission in flash photographing.
In this light emission control system by the TTL direct light detection, the light transmitted through the lens is detected. Thus, a precision of light emission control is higher than that of an external light emission system in which the light is detected by a photo-detector provided in a body of the electronic flash device to control the light emission. The TTL direct light system in very effective to proximate photographing.
However, since the light emission control system by the TTL direct light detection utilizes the reflection light from the film surface, the light emission characteristic varies with a reflection coefficient of the film which varies by a type of the film. Thus, proper exposure is obtained for a film of one type but the exposure may be over or under for a film of other type having the same film sensitivity.
For example, the reflection coefficients of a negative film and a positive film are different even if the film sensitivities are same. If the camera is set such that a proper exposure is obtained for the negative film, an overexposure results in for the positive film because the reflection coefficient of the positive film is lower.
This problem is applicable to not only the light emission control is the flash photographing mode by the TTL direct light detection but also the shutter control by the TTL direct light detection in the normal light photographing mode. If the reflection coefficients are different between different types of film although they have the same film sensitivity, a proper exposure may not obtained.